I feel you OP, RNG can be such a pain. My current game I had zero in the first two areas, 3 in the third, one in the fourth, and one in the fifth.

You can try going farther from your starting point and the swamp areas should get bigger, but also more dangerous since more two stars pop up and the swamp two stars will wreck you.

Then top that off with the RNG of crypts, you can find anywhere from 20-150 iron in a single crypt.

On the bright side, if you cleared the earlier swamps once you get the necklace from Bonemass you can go back through those areas and see if there is any hidden scrap piles.